1. Field of the Invention
The present invention relates to a discharging method for discharging a liquid material. In particular, the invention relates to a discharging method for a liquid material, to a discharging apparatus for a liquid material, and to an electronic device which can be manufactured thereby, which enhance uniformity of thickness of a film made by a discharged liquid material, and moreover, which prevents defects caused by static electrical charge of constituent elements on the substrate, which is easily electrostatically charged, or to a constituent elements to be formed on the substrate, which easily electrostatically charged.
2. Description of Related Art
Conventionally, as a discharging apparatus which is equipped with a discharging head which discharges a liquid material, an ink jet printer is known which is equipped with an ink jet head.
Typically, the ink jet head which is equipped on the ink jet printer, comprises a cavity which stores the liquid material, and a nozzle which is open to the cavity, and a discharging device which discharges the liquid material being stored in the cavity through the nozzle. In addition, a liquid material tank which stores liquid material is connected to the discharging head, and a liquid material is provided from this liquid material tank to the discharging head.
In addition, recently, not only for an commercial use ink jet printers, the ink jet head is also used as an industrial use discharging apparatus, that is, an apparatus which makes constituent elements of a wide variety of apparatuses. For example, the discharging head is used for forming color filters for liquid crystal apparatuses, etc., for light emission layers and for positive hole injection layers in organic EL element apparatuses, and in addition, for metal wiring of a wide variety of devices, microlenses, etc.
Here, in the case in which the ink jet head is used for manufacture of a color filter such as a crystal liquid apparatus, because the substrate is made of glass, the substrate may easily become charged, and in the case in which a color filter material jetted on a region which is charged, so-called “flight path curvature” may be occur, by which a discharged liquid droplet impacts a location which differs from the desired location.
Therefore, a color filter manufacturing method which avoids alteration of the impact point of liquid droplets by reducing the flight path curvature (for example, refer to Japanese Patent Application No. 11-281810 is desired.).
In this color filter manufacturing method, electrical charge on a substrate is neutralized by blowing ionized gas on the substrate before discharging a color filter material (ink), because the purpose is only to avoid charging the substrate itself. This is because the substrate is made of a material, such as glass, which easily becomes charged.
However, in the manufacturing process of a wide variety of devices other than color filter manufacturing, by charging an element except the substrate, for example, constituent elements of a device which are formed on the substrate, there may be a problem in that the element will be damaged or destroyed by electrostatic charge, or the ink jet head (discharging head) will be damaged or destroyed by the charge of the element.
No prior technology is provided for preventing charge build-up of the element except for the substrate itself.
Moreover, normally, at the ink jet head (discharging head), in the case in which a wide variety of films such as color film as a constituent elements of a device is formed, a thing which film material which is a solid component is dissolved or dispersed in a solvent is used. This is for adding fluidity to the film material and enables it to be provided to the nozzle, and to be discharged though the nozzle.
Therefore, by discharging a liquid material including a solvent or dispersing media on a substrate, and after coating it in thin film style, transferring it to a drying process, and conducting drying processing which evaporates the solvent and the dispersing media using a hot air furnace, hot plate, infrared radiation furnace, etc., forming it into film style constituent elements.
However, in the film made of the liquid material, evaporation of the solvent and the dispersing media occurs immediately after being coated on the substrate, and preliminary evaporation occurs before transferring it into the drying process. At the preliminary evaporation under atmospheric conditions, near the surface of the film, concentration of the solvent (dispersing media) steam evaporated from the film is high above the center portion and is relatively low at the periphery.
Then, the evaporation proceeds slowly at the center portion, and on the other hand, the evaporation proceeds relatively faster at the portion around it, and this causes circulation of the solvent (dispersing media) from the center portion side to the portion side around it. In the case in which circulation occurs, a part of the solid content (film material) moves from the center portion to the periphery, and as a result, film thickness at the portion around the center portion becomes thicker than the center portion.
Therefore, as might be expected, uniformity of the film thickness of entire of the film gotten after the drying process is lost, thus, dispersion of function in the constituent elements occurs, and this results in one cause which reduces the reliability.
In addition, like a color filter and an organic EL, in the case in which a number of films on a substrate by discharging an ink into a cell which is demarcated for each pixel, the center portion of the cell becomes concave if the drying period is short, while the center portion of the cell becomes convex if the drying period is relatively long. Therefore, in the case of viewing the entire substrate, convex shaped cells are clustered toward the center portion, whereas concave shaped cells are clustered around the periphery, and this causes variation in luminance of the panel.